Many people believe that religion began when God revealed himself to human beings at the time of their creation several thousand years ago. However, we now know that in fact the earth is 4.5 billion years old. With this knowledge in mind, how did religion begin and develop? In particular, how did Judaism and Christianity begin and evolve? This book explores the answers to these questions, particularly syncretism of religion, i.e. the merging and blending of religious ideas. Topics include paleolithic and neolithic religion, influences of Mesopotamia, Egypt and Persia on Judeo-Christian beliefs, "mystery religions", human sacrifice in Canaan, the axial age, and the origins of Yahweh.